Part Focus: Shock Absorbers, Springs / Brands: KYB, Moog, Neox,
World class shock absorber manufacturer KYB offers problem solving tips for common situations encountered when fitting struts.
The vehicle reacts unevenly or oddly over bumps. To ensure the vehicle performs safely and as designed, we recommend replacing shocks or struts in (left & right) pairs. When the damping rates are significantly different from side to side the vehicle body and wheel movement variations can cause handling abnormalities.
Over-tightening the upper strut shaft mounting nut causes damage. Do not use an air or electric impact wrench to tighten the upper mounting nut on the piston rod. This can make the torque higher than recommended and cause damage. Correct tightening is accomplished by holding the piston rod with a wrench or special tool (not vice grips or pliers) at the machined shoulder & using a torque wrench set to the vehicle manufacturer’s specification.
Does any fluid need to be put into the strut housing when replacing a cartridge-style strut? When installing a KYB strut cartridge do not put any water, oil or any other liquids inside of the struthousing. Any existing fluid should be removed from the housing before installing the new cartridge. KYB cartridges are designed and engineered to operate without any additional liquids.
The supplied small parts kit has too many or not all of the parts needed. Most shocks and struts come with a parts kit. This may include a nut, washers, spacers, or even a bumper. Before installing the shocks or struts please review all of the items contained in the parts kit. Due to vehicle application variations, the kit may contain more or fewer parts. Some OE components are meant to be re-used.
The original mounting stud nut does not thread correctly or damages the new KYB shock/strut upper mounting stud threads.
Always use the new nut supplied! When a threaded nut is included with the KYB shock or strut it is necessary to use the new nut: Do not re-use the old one. For production purposes and quality consistency, KYB may supply a special nut that matches the new mounting stud.
The replacement shock/strut has a shorter upper mounting stud. Mounting stud lengths may differ slightly, but all will mount correctly. The most common difficulty occurs when trying to install the mounting nut when the vehicle is not on the ground. This can cause the stud not to push all the through the mounting bushing and limit the exposed stud threads.
The shock stud appears too short or noises occur after installation. Always compare the supplied washers in the parts kit with the original components. Some parts kits contain more components than needed and some original washers are meant to be re-used. If the washer or spacer has a different thickness it may cause installation problems.
Noises After Shock/Strut Replacement: Causes. Internal shock or strut noise is uncommon. The most common cause for clunking noises over bumps is the mounts or attaching parts. Careful inspection is often required to identify the cause. Mountings and bushings can appear to be tight, but move slightly when driving. Viewing components when the suspension is hanging downward on a hoist may not reveal the cause. Replacing strut mounts is always recommended when replacing the struts. The insulating material density changes over time and the mount pivot bearings wear.
Other suspension and steering components often cause noises that the shocks/struts get blamed for: Ball joints, sway bar bushings & links are common causes. Hydraulic Fluid Leak: Causes. The main reason that shocks or struts leak is that the upper seals wear or become damaged causing hydraulic fluid to leak out of the top. Actually, vehicle use rarely causes leaks. There are several things that can cause seal wear; including:
Dirt and debris getting inside of the shock/strut: This often happens when the strut boot is torn or not sealed properly
A damaged strut shaft: If there is any damage, pitting or scoring on the polished shaft it will cause premature or rapid wear on the upper seals. It is critical not to use pliers on the polished shaft during installation as this can damage the shaft.
The new shock or strut appears shorter than the unit removed from the vehicle.
In some instances a competitor’s part number is longer than required by the vehicle manufacturer and in other cases the KYB product includes a performance improvement. Some KYB shocks include an improved internal bumper stop to cushion extreme movements. This may change the total length before installation; however, the function will be correct when installed on the vehicle. Some of the reasons include:
Protect potential damage from full extension of the unit
Reduce vehicle roll-over effects
On some applications it is necessary to raise the axle or suspension slightly to attach the shock mountings which is also common on many OE components.
Not enough stud threads visible to install or tighten the upper mounting nut.
Always make sure that the vehicle is on the ground before tightening the upper stud nut. This will push the stud further through the mounting bushing and avoid thread damage.
The left or right strut installs OK, but the other side won’t line up correctly. During installation, what sometimes appears to be a miss-positioned welded spring seat may actually be caused by the need to reposition the upper mount rubber insulator. To install some struts it may be necessary to rotate the upper strut mount insulator which can be separated from the mount. The directions are as follows:
Make a mark on the upper mount in line with (depending on the model) the notch in the strut pinch bolt area or the steering knuckle bracket.
Disassemble and loosen the spring compressor so you can remove the mount and insulator.
Separate the rubber insulator from the underside of the mount and then put the insulator back onto the spring so that the insulator matches the spring position.
Put the strut back into the spring and put the mount onto the insulator.
Align the mark on the mount to the notch in the strut or steering knuckle bracket.
Compress the mount and spring assembly, install and torque the strut nut to OEM specifications.
Reinstall the assembly
The strut started leaking fluid from the upper seal shortly after installation. Do not use pliers or vice grips on the polished shaft. The use of pliers can cause scoring the highly polished chrome shaft. This will cause leakage of oil from the unit.
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